Wireless communication systems are inherently insecure communication systems due to the fact that anyone may intercept a wireless signal. As a result, encryption techniques have been developed that prevent unauthorized users from intercepting and correctly decoding private conversations. However, typically encryption is agreed upon at the setting up of a call and merely involves an encryption of the over-the-air portions of the communication. When encrypted voice is received from a source mobile station by a wireless infrastructure, the encrypted voice is decrypted by an access network serving the source mobile station and conveyed over the infrastructure in an unencrypted format. The unencrypted voice is then again encrypted by a destination access network before being conveyed over-the-air to a destination mobile station.
For highly secure communications where two end terminals, such as two mobile stations or a mobile station and a landline telephone, may use a publicly-owned wireless infrastructure (as opposed to a privately-owned enterprise system) to engage in a non-public, high security call, conveyance of the call over the infrastructure in an unencrypted format may be unacceptable. In such communications, it may be desirable to have end-to-end encryption, where only the end terminals are able to decrypt the communications. In order to provide such end-to-end encryption, the encryption scheme used, and even the data format employed, should be transparent to the publicly-owned infrastructure. Further, situations may arise where it may be desirable for a conversation that is engaged in via a publicly-owned infrastructure and that begins in a non-encrypted mode to switchover to a secure, encrypted mode.
Therefore, a need exists for a method and apparatus for providing an end-to-end clear transport of encrypted payload, wherein the transporting of an encrypted payload over an intervening infrastructure is independent of the encryption format employed and the data format being used by the end terminals and that further provides the users of the mobile stations with an option to convert a non-encrypted call to an encrypted call during the course of the call.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help improve understanding of various embodiments of the present invention. Also, common and well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention.